WEDNESDAY, Sept. 8 (HealthDay News) -- Mutations in two genes may be associated with one of the most deadly types of ovarian cancer, U.S. researchers have found.

In the study, researchers at the Johns Hopkins Kimmel Cancer Center looked for mutations in 18,000 protein-encoding genes in ovarian clear cell tumors from eight patients. The investigators found 268 mutations in 253 genes, with an average of 20 mutations per tumor.

Further investigation revealed that two genes -- ARID1A and PPP2R1A -- were more commonly mutated than other genes. ARID1A mutations were present in 57% of tumors while PPP2R1A mutations were present in 7.1% of tumors, according to the report published in the Sept. 8 online edition of Science Express.

ARID1A is a gene whose product normally suppresses tumors. PPP2R1A is a gene that, when altered, helps turn normal cells into tumor cells. The genes had not previously been linked to ovarian cancer, the researchers explained in a news release from the Johns Hopkins Kimmel Cancer Center.

The findings "may provide opportunities for developing new biomarkers and therapies that target those genes," Nickolas Papadopoulos, associate professor of oncology and director of Translational Genetics at the Ludwig Center for Cancer Genetics & Therapeutics at the cancer center, said in the news release.

Ovarian clear cell carcinoma, which accounts for about 10% of cancers that start in cells on the surface of the ovaries, mainly affects women aged 40 to 80 and is resistant to chemotherapy, according to background information in the news release.